Process for rustproofing articles of iron and steel



Patented Nov. 19, 1929 UNITED STATES WLLLIAM H. ALLEN, OF DETROIT,MICHIGAN, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

PATENT OFFICE PARKER RUST PROOF COMPANY, OF DETROIT, MICHIGAN, ACORPORATION OF MICHIGAN PROCESS FOR RUSTPROOFING ARTICLES OF IRON ANDSTEEL No Drawing.

The present invention relates to a process ofrust proofing iron andsteel.

Among the objects of the invention is to modify the known processesinvolving the use of phosphorus compounds so as to greatly shorten thetime usually considered necessary for properly rust proofing the iron orsteel articles.

Heretofore phosphoric acid and phos- 1o phates of some of the metals inacid solution have been used for the purpose of producing on iron orsteel articles, a rust resisting coating and in such processes, it hasbeen considered necessary to heat the solution containing the articlesto boiling and to accurately control the conditions of the process,thereby utilizing considerable time in the treatment of a batch of thearticles.

In the present process, the articles are merely dipped in the rustproofing solution and allowed to remain only a short period, whereuponthey are removed'and brought to a moderately high temperature and thencooled and washed. These steps of this process consume only a smallfraction of the time required in the known processes.

, The solution which I have found desirable for the present purpose is adilute solution of ortho-phosphoric acid containing chromium phosphate.These solutions may be prepared in any suitable manner and shouldcontain about 2 phosphoric acid and about 175% of chromium combined asphosphate, these proportions are not fixed but may be varied to givegood results, although the proportions mentioned are preferred.

Free phosphoric acid up to several percent more will not materiallyinterfere with the results, while chromium in much larger amounts, evenup to one per cent or more, will also give good results.

In using the solution, the articles are dipped cold or only moderatelywarm, as heating of the solution to any great degree will causedeterioration thereof. The solution may be used slightly warm but shouldnot be allowed to heat to near its boiling point.

After the articles have been in the solu- Application filed August 11,1928. Serial No. 299,129.

tion for a very short period, they are taken out and heated to atemperature of approximately 450 F., to convert the chromium phosphateinto insoluble chromium pyrophosphate and after cooling, the articlesare then subjected to a washing or brushing step to remove the loosepowder of phosphate from the surface. 4

Iron or steel articles treated in the present process may be subjectedto severe tests without indication of rust.

Now having described the invention and the preferred form of embodimentthereof, it is to be understood that the said invention is to be limitednot to the specific details herein given but only by the scope of theclaims which follow.

I claim 1. The process of rust proofing iron or steel articles, whichcomprises dipping them into a solution containing chromium andphosphoric acid radical, and subsequently heating to a temperaturesuificient to convert the chromium phosphate into chromiumpyro-phosphate.

2. The process of rust proofing iron or steel articles, which comprisesdipping them into a dilute solution containing chromium and phosphoricacid radical, and subsequently heating to about 450 F.

3. The process of rust proofing iron or steel articles, which comprisesdipping them into a solution containing chromium phosphate and freephosphoric acid, then heating to about 450 F.

4:. The process of rust proofing iron or steel articles, which comprisesdipping them into a dilute solution containing chromium and phosphoricacid radical maintained well below the boiling point, and subsequentlyheating the articles to a temperature suflicient to convert the chromiumphosphate into chromium pyro-phosphate.

5. The process of rust proofing iron or steel articles, which comprisesdipping them into a solution containing chromium phosphate and freephosphoric acid maintained well below the boiling point, andsubsequently heating the articles to a temperature suflicient to convertthe chromium phosphate into chromium pyro-phosphate.

6. The process of rust proofing iron or steel articles, which comprisesdipping them into a solution containing about 175% chro- 5 mium aschromium phosphate and about 2.5% free ortho-phosphoric acid at atemperature below the boiling point, then heating the said articles toabout 450 F. and subsequently removing any loose powdery deposittherefrom.

WILLIAM H. ALLEN.

